If you need to delete uneditable contact properties in the Salesforce Information section please file a ticket with Support and include the internal names of the properties you want removed.
If you've deleted a property in error, you can restore it by creating a new custom property with the same internal name, property type, and options (if applicable). Navigate to your properties as directed above, then click Create a new property and enter the same Internal name, Field type, and options if you're recreating a dropdown select, multiple checkboxes, or radio select property. For additional information on creating new properties, check out this article.